<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        .top{
            height:50px;
            width:100%;
            background-color: aqua;
            position: fixed;
            left:0;
            top:0;
        }
        .con{
           background-color: chartreuse;
           height: 1000px;
           margin-top:50px;
           margin-bottom:50px;
        }
        .bottom{
            height:50px;
            width:100%;
            background-color: blue;
            position: fixed;
            left:0;
            bottom:0;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="top"></div>
        <div class="con">
            <h1>111</h1>
            <h3>333</h3>
        </div>
        <div class="bottom"></div>
    </div>
</body>
</html>